The use of fastening systems for securing the corners of disposable absorbent articles, such as diapers, is known. Such systems are used to provide a secure means for keeping such articles on the wearer during use. When such systems are refastenable, adjustments may be made during use to reposition the articles, to allow a caregiver to check for soiling, and may also be used to provide a secure means for keeping such articles and their soiled contents wrapped up after use until disposal.
A typical fastening system for use with absorbent articles may have a closure member (tab) and a landing member. The closure member (tab) may be disposed directly or indirectly upon the longitudinal edge of the body portion in either the front or back of the absorbent article waist regions. In use, the closure member (tab) may be secured to the landing member, which is disposed upon the correspondingly opposite body portion of the front or back of the absorbent article. A refastenable system may be provided with, e.g., hooks on the closure member (tab) that releasably engage loops disposed on the landing member. To improve fit, the end of the closure member (tab) that does not engage the loops in the landing member area, may be attached to one end of an elastic/stretch member (ear), and the other end of the elastic/stretch member may be secured to the longitudinal edge of the body portion of the absorbent article.
The inventors have found that after fastening, conventional absorbent articles having an elastic/stretch member (ear) connected to a closure feature (tab) have a tendency to neither distribute forces evenly within the elastic/stretch member (ear), nor adequately to provide sustained comfortable fit to the wearer. This is particularly apparent when the closure feature (tab) (of higher modulus) and the elastic/stretch member (ear) (of lower modulus), which together provide the force required and line of tension required to hold the absorbent article about the wearer, have an incomplete attachment in the vertical (relative to the wearer) direction. Modulus as described here refers to Young's modulus, typically described in units of either N/m2 or lbs/in2, and higher/lower means relative to each other. In this case, the closing of the closure system imparts a force through the high modulus portion of the closure system into and through the elastic/stretch member. Typically, the attachment of the closure feature (tab) to the elastic/stretch member (ear) is centered about the height of the closure feature (tab) along the line of attachment to the elastic/stretch member (ear). As the closure member (tab) is typically smaller in area than the elastic/stretch member (ear) and even then, only a portion of the closure member (tab) engages the elastic/stretch member, the areas of the elastic/stretch member (ear) that are attached to the higher modulus closure feature (tab) do not exhibit the same force or strain profile as those areas which are not attached to it. Without being bound by theory, Applicants believe that the impact on fit and comfort is that this causes tension lines to develop which can lead to localized discomfort and red marking due to the presence of rigosity caused by high tension bands.
Additionally, and again without wishing to be bound by theory, Applicants believe the elastic/stretch material (ear) in the conventional arrangement will, a la the Poisson effect, tend to rope and collapse to the height of the high modulus closure feature (tab), leading to reduced surface area coverage and less contact area for friction lock of the elastic/stretch member (ear) on the wearer's body for fit. On the molecular level, Poisson's effect is caused by slight movements between molecules and the stretching of molecular bonds within the material lattice to accommodate the stress. When the bonds elongate in the direction of load, they shorten in the other directions. Without being limited by theory, it is believed that this behavior multiplied many times throughout the material lattice is what drives the phenomenon.
Attempts to achieve good fit have been made previously; however, there is a need to improve over these. For example, U.S. Pat. No. 5,358,500 (Lavon, et al.) discloses tape tabs secured to a landing member that are shaped and oriented to provide a primary line of tension through the diaper at an angle to the lateral direction. However, it is desirable to direct more force than these tape tabs (which are angled in the portion of the tab not connected to the ear, but rectangular and straight in the portion of the tab connected to the ear) provide to the top area of the ear, and thereby, to the top/back of the diaper, to promote a more snug fit to the wearer. Also, U.S. Pat. No. 5,603,794 (Thomas) discloses angled tape tabs for use with disposable absorbent articles. However, it is desirable to direct more force than these angled tape tabs (which lack an intermediate portion that is whose top and bottom edges are not in-line with the top and bottom edges of the portion of the tab not connected to the ear and the portion of the tab connected to the ear) provide to the top area of the ear, and thereby, to the top/back of the diaper, to promote a more snug fit to the wearer. As such, there is a need for fastening systems that provide improved fit to the wearers of absorbent articles.